PROJECT SUMMARY/ABSTRACT The endogenous cannabinoid system (ECS) ? comprising the endocannabinoids, their G-protein coupled re- ceptors, and their metabolic enzymes ? is one of the most important physiological systems involved in estab- lishing and maintaining human health. In some illnesses, ECS dysregulation is an element of disease pathol- ogy whereas in others it is believed to be protective. Thus, there is intense interest in developing pharma- cotherapies that target the ECS to blunt its pathologies or harness its protective effects. One of the main challenges in developing new drugs that target the ECS is the problem of side effects, con- sistent with the nearly ubiquitous expression of this signaling system. Current efforts to increase the functional specificity of ECS drugs include preventing them from crossing the blood brain barrier, and targeting ancillary ECS proteins which modulate principal ECS components without being direct effectors themselves. Until now, discovery of ancillary proteins has proceeded mainly by inference from prior knowledge obtained from isolated cells. This approach can be limiting because knowledge of the underlying genetic and biochemical networks is usually incomplete. Here we propose to develop new high-throughput methodologies to enable the first unbi- ased genetic screens to identify new ECS molecules in the nematode Caenorhabditis elegans. C. elegans is an omnivorous bacterivore but it learns to prefer some species of bacteria more than others. We recently discovered that one of the worm's endocannabinoids increases the worm?s appetite for favored foods over less favored foods, a phenomenon called hedonic amplification. We propose this system as a genetically tractable model of cannabinoid effects on appetitive behavior, providing an easily screenable phenotype that directly corresponds to a well-known human behavior. The research develops two high-throughput microfluidic systems for quantifying hedonic amplification in C. ele- gans. The systems are then utilized to perform two small-scale genetic screens as a prelude to future large- scale screens. In the first, hedonic amplification will be quantified in strains in which homologs of known mam- malian ECS components have been knocked out; this screen further validates the C. elegans ECS as a mam- malian model. In the second screen, hedonic amplification will be assessed in a select set of wild isolate strains of C. elegans to estimate the heritability of this phenotype. The research is significant because it could ultimately lead to the discovery of novel drug targets to mitigate disease and promote health.